Port Costa, CA frost dates
Frost is light and occasional here — typically a few cold nights around midwinter (about 5 a year). Cover tender plants when frost is forecast.
How Port Costa compares
- In a typical year, frost nights in Port Costa fall between December 27 and January 17. In 1 year in 10 the first frost comes as early as December 4, or the last frost as late as March 4.
- Port Costa shares its weather station with Vallejo, CA, 10 km away, so the two have the same frost dates.
Frost probability
| Chance of frost after | Date |
|---|---|
| 90% (early) | December 23 |
| 50% (median) | January 17 |
| 10% (safe for tender plants) | March 4 |
| Chance of frost before | Date |
|---|---|
| 10% (early) | December 4 |
| 50% (median) | December 27 |
| 90% (late) | February 4 |
Frost here means 32°F (0°C). A median date means half of years have their last frost earlier and half later.
Gardening where frost is rare
Port Costa, CA only freezes on a few winter nights, so the usual "plant after the last frost" rule doesn't apply. Heat and rainfall decide the seasons instead:
- Cool-season crops (lettuce, broccoli, peas, carrots) grow best from fall through late winter.
- Warm-season crops (tomatoes, peppers, beans, squash) do best planted in late winter to spring, and again in late summer for a fall crop — midsummer heat can stop tomatoes setting fruit.
- Heat lovers (okra, sweet potatoes, melons) can be planted through spring and early summer.
About these dates
Based on 1991–2020 NOAA climate normals for the Vallejo, CA weather station, 6 km away (elevation 341 ft (104 m)).
Frost dates near Port Costa
- Crockett Jan 17 · Dec 27
- Benicia Jan 17 · Dec 27
- Rodeo Jan 17 · Dec 27
- Hercules Jan 17 · Dec 27
- Martinez Feb 28 · Nov 22
- Vallejo Jan 17 · Dec 27
- Pinole Jan 4 · Jan 2
- El Sobrante Jan 4 · Jan 2
- Pleasant Hill Jan 7 · Dec 19
- American Canyon Mar 5 · Nov 21
Frequently asked questions
When is the last frost in Port Costa, CA?
The median last spring frost in Port Costa, CA is January 17. There is still about a 10% chance of frost after March 4, so wait until then to plant frost-tender crops like tomatoes and peppers.
When is the first frost in Port Costa, CA?
The median first fall frost is December 27, with about a 10% chance of frost before December 4.
How long is the growing season in Port Costa, CA?
About 344 days between the median last spring frost and first fall frost.
What planting zone is Port Costa, CA?
Port Costa, CA is in USDA hardiness zone 9b.